21551222 has 16 divisors (see below), whose sum is σ = 40303872. Its totient is φ = 8396520.

The previous prime is 21551221. The next prime is 21551251. The reversal of 21551222 is 22215512.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21551194 and 21551203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21551221) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 69818 + ... + 70125.

It is an arithmetic number, because the mean of its divisors is an integer number (2518992).

Almost surely, 2^21551222 is an apocalyptic number.

21551222 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

21551222 is a deficient number, since it is larger than the sum of its proper divisors (18752650).

21551222 is a wasteful number, since it uses less digits than its factorization.

21551222 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 139963.

The product of its digits is 400, while the sum is 20.

The square root of 21551222 is about 4642.3293722010. The cubic root of 21551222 is about 278.2855355151.

Adding to 21551222 its reverse (22215512), we get a palindrome (43766734).

The spelling of 21551222 in words is "twenty-one million, five hundred fifty-one thousand, two hundred twenty-two".